The present invention relates to an end wall made of injection molded material for a wound roll. The end wall has a rectangular, in particular square, plate that has rounded corner surfaces. The front side of the plate, facing toward the wound roll, has a central plug-in peg and locking lugs, and the reverse side of the plate, facing outward away from the wound roll, is stiffened by radial and annular ribs. The side walls of the plate have stacking lugs that delimit stacking pockets that are at right angles to the plate. The stacking pockets are shaped in a manner complementary to the stacking lugs.
An end wall of this kind is known from Patent DE-PS 38 08 064 and U.S. Pat. Nos. 4,884,690 and 5,205,411. U.S. Pat. No. 4,884,690 and 5,205,411 are hereby expressly incorporated by reference.
An individual one-part end wall of this kind that is made of plastic or of another material that can be formed without cutting is intended for packaging material wound onto winding tubes, for example plastic films. The one-part end wall forms, together with a second, corresponding end wall, a dimensionally stable overall package for a wound roll.
From the known end wall described above, a number of vertically aligned end walls of ready-packaged wound rolls can be stacked with their side walls one next to the other or one above the other, as desired, and can be locked into engagement with respect to one another. This means that wound rolls ready-packaged by means of the end walls and encircling straps can be readily stacked one on top of the other. The ready-packaged wound rolls are usually stacked on wooden pallets. Here, it is found that, because of the smooth surfaces of the support faces of the stacking lugs, the side wall that is lying on the pallet and that is a part of the end wall has a low frictional grip with the pallet, so that the slipping resistance of a stack of this kind is not ensured. If, in particular, heavy wound rolls are packaged with such end walls, then, because of the low frictional grip and also because of the small support faces of the stacking lugs on the pallet and the high specific surface pressure that this entails, along with the high surface loading on the stacking lugs, there is increased risk of breakage and inadequate stability of the supported side wall.
German Utility Model 19 91 976 discloses a one-part end wall which is made of plastic and is composed of a quadrangular, preferably square, flat plate stiffened by radial webs. In the center is disposed a plug-in peg for the roll of wound material, which plug-in peg is equipped, for example, with holding prisms. The plate is encased by a strap, on the outer side of which small prismatic strips are arranged. At the corners of the plate, the strap encloses four cup-shaped depressions, which project into the free space between the wound material and packaging sleeve and are open near the outer end side, and the strap possesses a surrounding stop strip which is provided with teeth.
DE-OS 14 86 562 discloses a protective package for film rolls and metal rolls, which is composed of two similar flanges equipped with a hollow hub that can be inserted into the winding core of the roll. Each of these flanges has at least two outer edges or edge parts which are bordered parallel to one another and are equipped with incisions and tongues, by means of which, during stacking of a plurality of rolls one on top of the other, interlocking of the flange edges lying one above the other is achieved and mutual displacement of the stacked rolls is prevented. These flanges cannot be stacked arbitrarily, but only in a specific arrangement next to each other or one above the other and brought into engagement with one another.
GB Patent 1,497,929 describes square end walls for wound rolls, flanges being present along each side edge of an end wall and at right angles to the end wall. One of the four surrounding flanges has two projecting pegs whereas the opposite flange has two holes at the locations corresponding to the locations of the pegs. The stacking of the wound rolls takes place in rows, the upper row of the wound rolls being offset with respect to the lower row in such a manner that the pegs of one end wall are in engagement with the holes of two adjacent end walls lying therebelow, thus preventing a lateral displacement of the two rows of wound rolls with respect to one another.
In the case of the known end walls, the end walls can be stacked, without a wound roll, one above the other with further, horizontally aligned end walls. The vertically aligned end walls, in particular with the wound rolls, can only be stacked in a specific arrangement next to one another or one above the other and brought into engagement with one another. This means that ready-packaged wound rolls cannot readily be stacked directly one above the other, simply and reliably.
In the case of flat front sides of the end walls, compressions can occur in the soft, that is, loosely wound, edge region with respect to the core region of the wound roll, due to the slightly oblique position of the end walls with respect to the end surfaces of the wound roll. It is possible for the oblique position to occur as early as during packaging of the wound rolls with the end walls, or by the packaged wound rolls slipping during transport, loading or unloading.